Messi also believes the transfer will leave Madrid worse off and says Juve are now among the clear favourites to win this season's Champions League.

Ronaldo swapped Spain for Italy in a deal worth 100 million euros ($117 million) in July, after securing a third consecutive European crown, and his fourth in five years with Real.

But Messi, who missed out on a three-man shortlist for FIFA's world player of the year award on Monday, feels the balance may have shifted following the 33-year-old's exit.

"I was surprised, I didn't imagine him leaving Madrid or that he would go to Juve because there was talk of many clubs (interested). The truth is I was very surprised but Juve are also a very good team," Messi told Catalunya Radio.

"Real Madrid are one of the best teams in the world and they have a great squad but it's obvious the departure of Ronaldo makes them less strong while Juve have become a clear favourite for the Champions League.

"They already had a good team and now they also have Cristiano Ronaldo."

Madrid's dominance in Europe has made failure even harder to swallow for Barcelona, whose shock defeat by Roma in April meant crashing out in the quarter-finals for a third consecutive season.

Even winning both La Liga and the Copa del Rey last term for a domestic double was not enough to extinguish the disappointment.

"It's time to win the Champions League," Messi said. "We've been knocked out in the quarter-finals three seasons in a row and maybe the last one was the worst of all because of the result and how the match was played.

"I think we have to aim for that, as a club, as a team and as a collective. We have a spectacular squad and we can do it."

Ronaldo's move was the latest example of increasingly lavish spending by Europe's biggest clubs, with Neymar, Kylian Mbappe, Philippe Coutinho and Paul Pogba all snapped up for more than 100 million euros over the past two years.

Messi believes the lure of Barcelona and Real Madrid is now being neutralised by the mouth-watering sums on offer.

"There are clubs now with a lot of money and players move for that reason," he said.

"Wherever the most money is, that's where they end up going. Things have changed and now the owners of clubs are multi-millionaires.

"Before, everyone wanted to play for Barca or Madrid, who were the best, but now everything's tighter and there's not much of a difference between the teams in Manchester, PSG, Madrid, us, Bayern (Munich) and the Italian (teams)."

Barcelona signed four players this summer, with Arthur Melo, Clement Lenglet, Arturo Vidal and Malcom all arriving at the Camp Nou.

Messi singled out Arthur, the 22-year-old Brazilian playmaker, for special praise.

"If I have to say one, I'll go with Arthur, who surprised me because I did not know much about him," Messi said.

"He has a style very similar to Xavi's, he always wants the ball, does not lose it, plays short passes and is very reliable.